York U chemists reveal relativistic effects predicted 30 years ago
In a major development, Professor Emeritus Diethard Bohme in the Faculty of Science and his team published a trilogy of articles this year revealing relativistic effects in chemistry theorized 30 years ago by Finnish chemist Pekka Pyykkö.
Relativistic effects occur when an atom has a high positive nuclear charge, as is the case in heavier atoms. According to theory, the higher positive charge causes electrons to orbit the nucleus at very high speeds approaching the speed of light and to increase in mass (the relativistic effect). This results in a reconfiguration of the atomic orbitals and can lead to stronger bonding with other atoms or molecules. The relativistic effects are predicted to be particularly large for gold and its neighbors on the periodic table, platinum and mercury (see figure below).
Bohme’s team measured the onset of relativistic effects by measuring rates of bond formation. Their discovery was made unexpectedly during a broader systematic study of how metals react, when they noticed an odd trend in reactivity as they went down the periodic table. The measured rates of chemical bond formation between metal ions and molecules were observed to increase for the atomic ions of platinum, gold and mercury as they went down the periodic table, just as predicted by theory.
“Our results further our understanding of fundamental aspects of chemical bonding between metal atoms and molecules, and even of applications in which such interactions are exploited, such as in catalytic converters and hydrogen fuel combustion in automobiles,” said Bohme.
The research was performed in collaboration with Bohme’s former PhD students Vitali Lavrov and Voislav Blagojevic and research associate Gregory Koyanagi. It was published in the International Journal of Mass Spectrometry in the following papers:
- Ligation kinetics as a probe for relativistic effects: Ligation of atomic coinage metal cations with ammonia
- Ligation kinetics as a probe for relativistic effects in ion chemistry: Gas-phase ligation of late atomic transition metal cations with OCS and CH3Cl at room temperature
- Ligation kinetics as a probe for relativistic effects in ion chemistry: Gas-phase ligation of Ni+, Pd+ and Pt+ at room temperature.
The insights from this research may well appear in undergraduate textbooks in chemistry in the near future.